The present invention was developed in view of a vexing energy loss problem in steam systems, but is not limited to that environment.
In conventional systems, as steam transfers its heat energy to a load it condenses. A steam trap discharges this condensate, while retaining the steam within the system. However, as the steam trap wears out, it increasingly loses steam and wastes energy.
Three known methods have commonly been used in an attempt to determine the steam loss of a steam trap.
1. Visual requires the discharge of the trap to the atmosphere for observation. However, atmospheric discharge is not always possible, due to the way that the trap has been installed into a condensate return system.
Moreover, with several different types of steam traps on the market, visual observation requires considerable training and skill. While it may be possible to detect a gross trap failure, estimating the magnitude of any steam losses cannot be done accurately as the following table illustrates (in which table #/hr. indicates pounds per hour).
______________________________________ Trap at 150 psig At Atmospheric Discharge Changes to Discharges Pressure Mass Flow Volume Flow ______________________________________ 1. 82 #/hr. Cond. 68.6 #/hr. Cond. 1.15 cu. ft./hr. Cond. 0 #/hr. Steam 13.4 #/hr. Steam 360 cu. ft./hr. Steam 2. 50 #/hr. Cond. 41.6 #/hr. Cond. .695 cu. ft./hr. Cond. 5 #/hr. Steam 13.4 #/hr. Steam 360 cu. ft./hr. Steam ______________________________________
In the table above, Trap 1 has no steam loss, but actually discharges a considerable amount of steam at atmospheric pressure due to flashing of the condensate as the pressure is reduced. As the human eye actually sees a volume flow, in the above example a large cloud of steam and a few drops of water would be seen.
On the other hand, Trap 2, which is defective and has a steam loss, discharges the same volume of steam as Trap 1 but a somewhat smaller volume of condensate. However, the human eye would be very hard pressed to determine which of these two traps actually had a steam loss.
2. In some areas it has been common practice to test traps by reading upstream and downstream trap temperatures with a pyrometer. If the temperature difference is very high, the trap has been considered satisfactory, while if the temperature difference is very low, the trap has been considered defective.
This tends to be a very dubious method as the outlet temperature follows the saturation temperature/pressure relation for steam. A trap with a high rate of steam loss, discharging to a much lower pressure, will display a very high temperature difference. On the other hand, a good trap, discharging through a very low pressure difference, will display very low temperature difference. In actual field service with a condensate return system, the trap outlet pressure is seldom, if ever, known. Accordingly, such temperature difference readings can be highly misleading as to the condition of the trap.
3. A highly trained person using a stethoscope or an ultrasonic device can inspect a trap for steam loss. However, considerable skill and training is required to understand the normal mode of operation of all the various available traps and to be able to distinguish abnormal operation. Sound devices generally can only be used to make a good/bad judgment of trap operation, and cannot accurately quantify the magnitude of a steam loss.
Accordingly, such known prior methods have not been entirely satisfactory.
Energy loss detecting apparatus, which is free of the foregoing limitations of the above-discussed known prior methods, was developed in a continuing program of development by personnel of the present Assignee corporation and is disclosed in U.S. Pat. No. 4,305,548 issued Dec. 15, 1981 and in PCT application No. U.S. 81/00025 filed Jan. 9, 1981 which was timely converted to U.S. National application Ser. No. 303,251 on Sept. 2, 1981. Such apparatus included a separator casing provided with baffles for the purpose of separating incoming steam and condensate flow and a flow sensor in the steam flow therein, the separator casing being interposable in a steam flow path between, for example, a steam consuming device fed from a steam source and a steam trap downstream of the consuming device.
While the apparatus disclosed in the aforementioned patent and applications has proved to be generally satisfactory, the present invention has been developed as part of a continuing development program to improve the structure and performance thereof.
Accordingly, the objects of the present invention include provision of energy loss detecting apparatus which enhances separation and permits substantial reduction in separator volume for high steam flow rates without loss of measurement reliability, which improves measurement reliability in the presence of pressure irregularities in the flow path outside the separator, and which reduces degradation of steam flow measurement liability due to collection of liquid droplets on interior parts of the separator.